Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07K—PEPTIDES
  • C07K14/00—Peptides having more than 20 amino acids; Gastrins; Somatostatins; Melanotropins; Derivatives thereof
  • C07K14/195—Peptides having more than 20 amino acids; Gastrins; Somatostatins; Melanotropins; Derivatives thereof from bacteria
  • C07K14/20—Peptides having more than 20 amino acids; Gastrins; Somatostatins; Melanotropins; Derivatives thereof from bacteria from Spirochaetales (O), e.g. Treponema, Leptospira
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
  • G01N33/48—Biological material, e.g. blood, urine; Haemocytometers
  • G01N33/50—Chemical analysis of biological material, e.g. blood, urine; Testing involving biospecific ligand binding methods; Immunological testing
  • G01N33/53—Immunoassay; Biospecific binding assay; Materials therefor
  • G01N33/569—Immunoassay; Biospecific binding assay; Materials therefor for microorganisms, e.g. protozoa, bacteria, viruses
  • G01N33/56911—Bacteria
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
  • G01N33/48—Biological material, e.g. blood, urine; Haemocytometers
  • G01N33/50—Chemical analysis of biological material, e.g. blood, urine; Testing involving biospecific ligand binding methods; Immunological testing
  • G01N33/53—Immunoassay; Biospecific binding assay; Materials therefor
  • G01N33/569—Immunoassay; Biospecific binding assay; Materials therefor for microorganisms, e.g. protozoa, bacteria, viruses
  • G01N33/571—Immunoassay; Biospecific binding assay; Materials therefor for microorganisms, e.g. protozoa, bacteria, viruses for venereal disease, e.g. syphilis, gonorrhoea
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07K—PEPTIDES
  • C07K2319/00—Fusion polypeptide
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07K—PEPTIDES
  • C07K2319/00—Fusion polypeptide
  • C07K2319/40—Fusion polypeptide containing a tag for immunodetection, or an epitope for immunisation
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N2333/00—Assays involving biological materials from specific organisms or of a specific nature
  • G01N2333/195—Assays involving biological materials from specific organisms or of a specific nature from bacteria
  • G01N2333/20—Assays involving biological materials from specific organisms or of a specific nature from bacteria from Spirochaetales (O), e.g. Treponema, Leptospira
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N2800/00—Detection or diagnosis of diseases
  • G01N2800/26—Infectious diseases, e.g. generalised sepsis

Definitions

• the invention relates to the field of recombinant antigens, and more particularly to a Treponema pallidum triplet antigen construct and its use in
• Treponema pallidum T. pallidum
• TP Treponema pallidum
• ELISAs enzyme-linked immunosorbent assays
• TP47 recombinant antigens
• membrane- integrated proteins 47kDa, 17kDa and 15kDa TP47, TP 17, and TP 15, respectively
• TP47 membrane- integrated proteins 47kDa, 17kDa and 15kDa
• TP47, TP 17, and TP 15, respectively membrane- integrated proteins 47kDa, 17kDa and 15kDa
• TP47, TP 17, and TP 15, respectively membrane- integrated proteins 47kDa, 17kDa and 15kDa
• the invention provides a recombinant plasmid encoding a
• the plasmid comprises nucleic acid encoding an amino acid sequence selected from the group consisting of SEQ ID NO:7, SEQ ID NO:8, SEQ ID NO:9, SEQ ID NO: 10, SEQ ID NO:l l, and SEQ ID NO: 12.
• the invention further provides a recombinant plasmid encoding a
• Treponema pallidum triplet antigen the recombinant plasmid selected from the group consisting of: the plasmid designated p261nS-TP17-15-47 and deposited with the American Type Culture Collection ("ATCC") as ATCC Accession No. PTA-11590 on January 12, 2011; the plasmid designated p261nS-TP47-17-15 and deposited with the American Type Culture Collection as ATCC Accession No.
• ATCC American Type Culture Collection
• the invention provides the Treponema pallidum triplet antigen having an amino acid sequence selected from the group consisting of SEQ ID NO:7, SEQ ID NO:8, SEQ ID NO:9, SEQ ID NO:10, SEQ ID NO: 11, and SEQ ID NO: 12.
• a method of detecting the presence of Treponema pallidum antibodies in a sample is further provided, which uses the Treponema pallidum triplet antigen, as well as kits for such detection.
• FIG. 1 illustrates the reaction scheme for the VITRO S ® Syphilis TP A test
• FIG. 2 shows the plasmid map of pUC57-TP1 ;
• FIG. 3 shows the plasmid map of pUC57-TP17
• FIG. 4 shows the plasmid map of pUC57-TP47
• FIG. 5 shows the plasmid map of pUC57-hSOD
• Fig. 6 shows the TP construct for cloning into pBlOG
• Fig. 7 shows the hSOD construct for cloning into a pBlOG triplet plasmid
• Fig. 8 shows the plasmid map of pBlOG
• Fig. 9 shows the plasmid map of pB10G-TP(l);
• Fig. 10 shows the plasmid map of pB10G-TP(2)
• FIG. 11 shows the plasmid map of pB10G-TP(3)
• Fig. 12 shows the TP(1) construct for cloning into pB10G-TP(2)
• FIG. 13 shows the plasmid map of pB10G-TP(l-2);
• Fig. 14 shows the TP(3) construct for cloning into pB10G-TP(l-2);
• Fig. 15 shows the plasmid map of pB10G-TP(l-2-3);
• Fig. 16 shows the plasmid map of pB10G-TP(l-2-3) with the unique restriction enzyme site
• Fig. 17 shows the plasmid map of p261nS-TP(l-2-3);
• Fig. 18 illustrates the direct assay format according to the subject invention.
• Fig. 19 illustrates the indirect assay format according to the subject invention.
• the assay (detection method) of the subject invention uses recombinant
• Treponema pallidum (the causative agent of Syphilis) outer membrane protein antigens to detect patient sample anti-IgG, anti-IgM, and anti-IgA antibodies.
• the recombinant protein antigens of interest are a 15 kilodalton antigen (TP 15), a 17 kilodalton antigen (TP 17), and a 47 kilodalton antigen (TP47).
• TP 15 15 kilodalton antigen
• TP 17 17 kilodalton antigen
• TP47 47 kilodalton antigen
• a fused recombinant antigen construct has been developed which incorporates the three antigens of interest as well as human copper zinc superoxide dismutase (hSOD).
• a 10 amino acid tag (the "261 sequence") is present at the N-terminus of the fused antigen construct to facilitate evaluation by Western blot and ELISA, and to provide a means for affinity purification if desired.
• the assay of the subject invention uses this fused recombinant antigen construct.
• the assay is the VITROS ® Syphilis TPA test and the assay is performed using the VITROS ® ECi/ECiQ Immunodiagnostic Systems,
• VITROS ® 3600 Immunodiagnostic System, or VITROS ® 5600 Integrated System using Intellicheck ® Technology Each of these analyzers is available from Ortho-Clinical Diagnostics, Inc., 100 Indigo Creek Drive, Rochester, NY 14626.
• An immunometric immunoassay technique is used, which involves the reaction of IgG, IgM or IgA antibodies present in the sample with a biotinylated recombinant TP antigen and a horseradish peroxidase (HRP)-labeled recombinant TP antigen conjugate.
• HRP horseradish peroxidase
• the antibody- antigen complex is captured by streptavidin on the wells (SAC wells). Unbound materials are removed by washing.
• the bound HRP conjugate is measured by a luminescent reaction.
• a reagent containing luminogenic substrate a luminol derivative and a peracid salt
• an electron transfer agent is added to the wells.
• the HRP in the bound conjugate catalyzes the oxidation of the luminol derivative, producing light.
• the electron transfer agent a substituted acetanilide
• the bound HRP conjugate is directly proportional to the concentration of anti-TP antibody present. This reaction scheme is illustrated in Fig.
• 10 represents the streptavidin coasted well
• 12 represents the biotinylated TP antigen
• 14 represents the antibodies to TP antigens present in a sample
• 16 represents HRP labeled TP antigen
• 18 represents signal reagent with enhancer
• 20 represents luminescence.
• Superoxide dismutase is present in the assay biotin reagent formulation to block binding of anti-SOD antibodies that may be present in the patient sample. This prevents a false reactive signal from being generated.
• the invention provides a recombinant plasmid encoding a Treponema pallidum triplet antigen.
• the plasmid comprises nucleic acid encoding an amino acid sequence selected from the group consisting of SEQ ID NO:7, SEQ ID NO:8, SEQ ID NO:9, SEQ ID NO: 10, SEQ ID NO: 11, and SEQ ID NO: 12.
• the plasmid is designated p261nS-TP17-15-47 and is deposited with the American Type Culture Collection ("ATCC") as ATCC Accession No. PTA-11590.
• Plasmid p261nS-TP17-15-47 includes nucleic acid having the nucleotide sequence as shown in SEQ ID NO:3, encoding the triplet antigen construct having the amino acid sequence as shown in SEQ ID NO:9.
• amino acids 5-14 encode the 261 tag
• amino acids 17-150 encode TP17 amino acids 155-277 encode TP 15, amino acids 282-695 encode TP47
• amino acids 697-849 encode hSOD.
• the plasmid is designated p261nS-TP47-17-15 and is deposited with the American Type Culture Collection as ATCC Accession No. PTA-11589.
• Plasmid p261nS-TP47-17-15 includes nucleic acid having the nucleotide sequence as shown in SEQ ID NO:6, encoding the triplet antigen construct having the amino acid sequence as shown in SEQ ID NO: 12.
• amino acids 5-14 encode the 261 tag
• amino acids 17-430 encode TP47
• amino acids 435-568 encode TP17
• amino acids 573-695 encode TP15 amino acids 697-849 encode hSOD.
• the plasmid is designated p261nS-TP 17-47- 15.
• Plasmid p261nS-TP17-47-15 includes nucleic acid having the nucleotide sequence as shown in SEQ ID NO:4, encoding the triplet antigen construct having the amino acid sequence as shown in SEQ ID NO: 10.
• amino acids 5-14 encode the 261 tag
• amino acids 17-150 encode TP17
• amino acids 155-568 encode TP47
• amino acids 571-693 encode TP15
• amino acids 695-847 encode hSOD.
• the plasmid is designated p261nS-TP47-15-
• Plasmid p261nS-TP47-15-17 includes nucleic acid having the nucleotide sequence as shown in SEQ ID NO:5, encoding the triplet antigen construct having the amino acid sequence as shown in SEQ ID NO: l 1.
• amino acids 5-14 encode the 261 tag
• amino acids 17-430 encode TP47
• amino acids 435-557 encode TP15
• amino acids 560-693 encode TP17
• amino acids 695-847 encode hSOD.
• the plasmid is designated p261nS-TP15-17-
• Plasmid p261nS-TP15-17-47 includes nucleic acid having the nucleotide sequence as shown in SEQ ID NO: l, encoding the triplet antigen construct having the amino acid sequence as shown in SEQ ID NO:7.
• amino acids 5-14 encode the 261 tag
• amino acids 17-139 encode TP 15
• amino acids 143-276 encode TP17
• amino acids 281-694 encode TP47
• amino acids 696-848 encode hSOD.
• the plasmid is designated p261nS-
• Plasmid p261nS-TP1 -47-17 includes nucleic acid having the nucleotide sequence as shown in SEQ ID NO:2, encoding the triplet antigen construct having the amino acid sequence as shown in SEQ ID NO:8.
• amino acids 5-14 encode the 261 tag
• amino acids 17-139 encode TP 15
• amino acids 143-556 encode TP47
• amino acids 559-692 encode TP17
• amino acids 694-846 encode hSOD.
• the ATCC is located at 10801 University Boulevard, Manassas, Virginia
• Each Treponema pallidum triplet antigen construct includes three
• Treponema pallidum antigens TP15, TP17, and TP47. While each has been defined by its amino acid sequence as well as a nucleotide sequence, it should be readily apparent that nucleotide additions, deletions, and/or substitutions, such as those which do not affect the translation of the DNA molecule, are within the scope of a particular nucleotide sequence (i.e. the amino acid sequence encoded thereby remains the same). Such additions, deletions, and/or substitutions can be, for example, the result of point mutations made according to methods known to those skilled in the art.
• nucleotide which alters the amino acid sequence encoded thereby, where the amino acid substituted is a conservative substitution or where amino acid homology is conserved. It is also possible to have minor nucleotide additions, deletions, and/or substitutions which do not alter the function of the resulting triplet (i.e. its ability to detect anti-TP15, anti-TP17, and/or anti-TP47 antibodies).
• Amino acid additions, deletions, and/or substitutions which do not negate the ability of the resulting triplet to detect anti-TP 15, anti-TP 17, and/or anti-TP47 antibodies are thus within the scope of a particular amino acid sequence.
• Such additions, deletions, and/or substitutions can be, for example, the result of point mutations in the DNA encoding the amino acid sequence, such point mutations made according to methods known to those skilled in the art.
• Substitutions may be conservative substitutions of amino acids. Two amino acid residues are conservative substitutions of one another, for example, where the two residues are of the same type.
• proline, alanine, glycine, serine, and threonine, all of which are neutral, weakly hydrophobic residues, are of the same type.
• Glutamine, glutamic acid, asparagine, and aspartic acid, all of which are acidic, hydrophilic residues, are of the same type.
• Another type of residue is the basic, hydrophilic amino acid residue, which includes histidine, lysine, and arginine.
• the presently preferred vector system for provision of the nucleic acid encoding the triplet antigen construct is a plasmid vector
• other vector systems can also be used.
• the presently preferred host cell for expression of the triplet antigen construct is the bacterial host cell Escherichia coli
• any suitable host and/or vector system can be used to express the triplet antigen construct.
• Other suitable bacterial hosts, yeasts hosts (such as Saccharomyces cerevisiae), as well as mammalian (for example, Hela cells, Cv-1 cells, COS cells) and insect hosts (such as Drosophila cell lines), can be used.
• Techniques for introducing the nucleic acid molecules into the host cells may involve the use of expression vectors which comprise the nucleic acid molecules. These expression vectors (such as plasmids and viruses; viruses including bacteriophage) can then be used to introduce the nucleic acid molecules into the suitable host cells. For example, DNAencoding the triplet antigen can be injected into the nucleus of a host cell or transformed into the host cell using a suitable vector, or mR A encoding the triplet antigen can be injected directly into the host cell, in order to obtain expression of triplet antigen in the host cell.
• expression vectors such as plasmids and viruses; viruses including bacteriophage
• DNA is injected directly into the nucleus of cells through fine glass needles (or RNA is injected directly into the cytoplasm of cells).
• DNA can be incubated with an inert carbohydrate polymer (dextran) to which a positively charged chemical group (DEAE, for diethylaminoethyl) has been coupled.
• DEAE positively charged chemical group
• the DNA sticks to the DEAE-dextran via its negatively charged phosphate groups.
• DNA evades destruction in the cytoplasm of the cell and escapes to the nucleus, where it can be transcribed into RNA like any other gene in the cell.
• cells efficiently take in DNA in the form of a precipitate with calcium phosphate.
• electroporation cells are placed in a solution containing DNA and subjected to a brief electrical pulse that causes holes to open transiently in their membranes. DNA enters through the holes directly into the cytoplasm, bypassing the endocytotic vesicles through which they pass in the DEAE-dextran and calcium phosphate procedures (passage through these vesicles may sometimes destroy or damage DNA).
• DNA can also be incorporated into artificial lipid vesicles, liposomes, which fuse with the cell membrane, delivering their contents directly into the cytoplasm.
• DNA is absorbed to the surface of tungsten microprojectiles and fired into cells with a device resembling a shotgun.
• viral vectors Since viral growth depends on the ability to get the viral genome into cells, viruses have devised clever and efficient methods for doing it.
• One such virus widely used for protein production is an insect virus, baculovirus. Baculovirus attracted the attention of researchers because during infection, it produces one of its structural proteins (the coat protein) to spectacular levels. If a foreign gene were to be substituted for this viral gene, it too ought to be produced at high level.
• Baculovirus like vaccinia, is very large, and therefore foreign genes must be placed in the viral genome by
• the gene of interest is cloned in place of the viral coat protein gene in a plasmid carrying a small portion of the viral genome.
• the recombinant plasmid is cotransfected into insect cells with wild-type baculovirus DNA.
• the plasmid and viral DNAs recombine through homologous sequences, resulting in the insertion of the foreign gene into the viral genome.
• Virus plaques develop, and the plaques containing recombinant virus look different because they lack the coat protein. The plaques with recombinant virus are picked and expanded.
• This virus stock is then used to infect a fresh culture of insect cells, resulting in high expression of the foreign protein.
• baculovirus vectors see Miller [Bioessays 11 :91-95 (1989)].
• viral vectors have also been used to transform mammalian cells, such as bacteriophage, vaccinia virus, adenovirus, and retrovirus.
• Host cells into which the nucleic acid encoding the triplet antigen has been introduced can be used to produce (i.e. to functionally express) the triplet antigen.
• the subject invention further provides a Treponema pallidum triplet antigen having an amino acid sequence selected from the group consisting of SEQ ID NO:7, SEQ ID NO:8, SEQ ID NO:9, SEQ ID NO:10, SEQ ID NO: 11, and SEQ ID NO: 12.
• Presently preferred embodiments of the triplet antigen are those represented by SEQ ID NO:9 and SEQ ID NO:12. These embodiments present the TP17 portion of the triplet before the TP 15 portion of the triplet, and higher antibody detection sensitivity is achieved with these constructs.
• All constructs include a leader sequence (presently preferred is a ten amino acid leader sequence (tag 261), though other suitable leaders could be substituted). All constructs further include human copper zinc superoxide dismutase (hSOD), a low immunogenic protein, at the carboxy terminus. Eleven lysine residues in the hSOD provide sites for biotin attachment and HRP conjugation, and two cystein residues are mutated to serine (Cys 4 and Cys 112) to prevent interchain protein polymerization [Hallewel et al, J Biol Chem 264:5260-5268 (1989)]. This construct is thus optimized for in vitro diagnosis of syphilis infection. Other suitable low
• the triplet antigen is under the control of the T5 promoter.
• Treponema pallidum antibodies in a sample are disclosed below, generally the method comprises: contacting a sample with the Treponema pallidum triplet antigen of the subject invention, wherein Treponema pallidum antibodies present in the sample bind to the Treponema pallidum triplet antigen forming an antibody/antigen complex; and detecting the antibody/antigen complex, thereby detecting the presence of the Treponema pallidum antibodies.
• the antigen triplet may be labeled with a detectable marker.
• Suitable markers include, for example, enzymatic labels such as horseradish peroxidase or alkaline phosphatase, as well as fluorescent labels (such as fluorescein, rhodamine, and green fluorescent protein).
• the assay format may also utilize biotin/avidin/streptavidin in the provision of the triplet antigen bound to a solid phase.
• Suitable solid phases include, for example, any non-aqueous matrix to which the triplet antigen can be bound.
• Such solid phases are well known in the immunoassay arts, and include, for example, polystyrene plates, polyacrylamides, glass, polysaccharides, polyvinyl alcohol and silicones.
• Microslides, microwells, and microtips are all used as solid phases in immunoassays.
• the assay format may involve direct detection of the antibody/antigen complex (see Fig. 18), which can comprise: contacting the antibody/antigen complex with a second Treponema pallidum triplet antigen of the subject invention, wherein the second Treponema pallidum triplet antigen is labeled with a detectable marker (HRP as shown).
• HRP detectable marker
• the assay format may involve indirect detection of the antibody/antigen complex (see Fig. 19), which can comprise: contacting the antibody/antigen complex with labeled anti-human antibody (monoclonal mouse anti-human antibody as shown).
• labeled anti-human antibody binds to the antibody present in the antibody/antigen complex forming an antigen/antibody/labeled anti-antibody complex, which is then detected thereby detecting the presence of Treponema pallidum antibodies in the sample.
• the sample can be any suitable sample (for example, serum, plasma, and EDTA or heparin plasma) but is preferably a serum sample.
• the Treponema pallidum triplet antigen construct of the subject invention can thus be utilized as a component of a kit for detection of Treponema pallidum antibodies.
• a kit is provided which comprises the Treponema pallidum triplet antigen construct, and additionally a second Treponema pallidum triplet antigen construct labeled with a detectable marker (an "enzyme conjugate" such as HRP-labeled Treponema pallidum triplet antigen)(see above discussion of markers).
• the kit can also comprise suitable positive and/or negative controls, calibration samples, enzyme conjugates, substrate for enzyme conjugates (such as O-phenylenediamine), buffer solution, and washing solution.
• T. pallidum outer membrane protein genes TP15, TP17, and TP47 were each synthesized based on amino acid sequence PI 6055 (amino acid 19- 141), P29722 (amino acid 23-156) and P29723 (amino acid 21-434), respectively, published in the central database UniProt (http://www.uniprot.org).
• hSOD Human copper zinc superoxide dismutase gene was synthesized based on amino acid sequence P00441 (amino acid 2-154), except two Cystein residues (amino acid 7 and 112) were mutated to Serine to prevent polymerization. All four synthesized gene codons were optimized for bacterial expression and each was inserted at the EcoR V site on host plasmid pUC57. The resulting plasmids, pUC57-15, pUC57-17, pUC57-45, and pUC57- hSOD, are shown in Figs. 2-5, respectively.
• TP genes from pUC57 were digested by Bgl II and Apa I (see Fig. 6 for resulting TP construct) and separately cloned into BamH I and Apa I sites of a previously constructed expression vector, pBlOG (see Fig. 8), which contained a T5 promoter, an ATG start site, and unique restriction sites EcoR I, BamH I, Apa I and Hind III.
• This generated three expressional vectors pB10G-TP15, pB10G-TP17 and pB10G-TP47 (shown generically as pBlOG- TP(1), pB10G-TP(2), and pB10G-TP(3) in Figs. 9-11, respectively).
• the TP doublet was created by subcloning. To construct a TP doublet subclone (see Fig. 13), a DNA gene insert was produced by PCR reaction using the second antigen expression vector as template and a pair of forward and reverse primers.
• the forward primer covered the EcoR I site, located in the T5 promoter region, upstream of the TP gene.
• the reverse primer matched the end of the TP gene and converted the Apa I site to a Bgl II site.
• This PCR product was then digested with EcoR I/Bgl II (see Fig. 12 for resulting TP-1 construct) and cloned into another antigen expression vector which was cut open with EcoR I and BamH I. Likewise, ligation of the compatible Bgl II on the insert and the BamH I on the host eliminated both restriction enzyme sites.
• TP Triplet Construction To produce six final triplet fusion genes, four TP doublet vectors, pB10G-TP17-TP47, pB10G-TP15-TP47, pB10G-TP47-TP15 and pB10G-TP17-TP15, were used as the host and the third TP gene was either added at the 5 'end of the TP doublet or added at the 3 'end of the TP doublet.
• the TP(l-2) double vector is shown generically in Fig. 13 and the TP(3) construct for insertion into the doublet vector is shown in Fig. 14.
• a DNA gene insert was produced by PCR reaction using the third antigen expression vector as template and a pair of forward and reverse primers.
• the forward primer matched the 5' end of TP gene and contained a Apa I site.
• the reverse primer matched the 3' end of TP gene and contained a Hind III site. This PCR product was then digested with Apa I/Hind III and cloned into the doublet expression vector which was cut open with the appropriate restriction enzymes.
• Triplets pB10G-TP15-TP17-TP47, pB10G-TP17-TP15-TP47 and pB10G-TP47-TP17-TP15 were made by adding the third TP gene at the doublet 5 'end, while triplets pB10G-TP15-TP47-TP17, pB10G-TP47-TP15-TP17 and pB10G-TP17-TP47-TP15 were made by adding the third TP gene at the doublet 3' end.
• PCR primers used in creating the doublets and triplets are listed in Table 4, PCR Primers, Group A. This triplet construct is shown generically in Fig. 15.
• SOD fusion tag (shown generically in Fig. 17) was created through “two-round” PCR and cloning. "Two-round PCR” was performed to link the C-terminal TP3 with SOD (see Fig. 7 for SOD construct) and to introduce restriction enzyme sites for cloning.
• the first round of PCR was composed of two separate PCR reactions, with the reverse primer (Table 4, PCR Primers, Group B) in one PCR reaction complementing the forward primer (Table 4, PCR Primers, Group C) in the other PCR reaction.
• the two products from the first round PCR were combined and amplified with a third set of nested primers (Table 4, PCR Primers, Group D).
• the forward primer matched the TP3 sequence and contained a unique restriction enzyme (RE) site.
• the reverse primer matched the 3 'end SOD.
• Two stop codons and a Hind III site created a new DNA insert (see Fig. 16).
• the new PCR product was digested and directly cloned into a pB10G-TP triplet plasmid digested at the designed unique restriction site and the Hind III site to yield pB10G-TP(l-2-3)-SOD (see Fig. 17).
• TPl, TP2, and TP3 represent the three T.
• TPl could be TP15
• TP2 could be TP17
• TP3 could be TP47
• Other combinations include: TPl could be TP15, TP2 could be TP47, and TP3 could be TP17; TPl could be TP17, TP2 could be TP15, and TP3 could be TP47; TPl could be TP17, TP2 could be TP47, and TP3 could be TP15; TPl could be TP47, TP2 could be TP15, and TP3 could be TP17; and TPl could be TP47, TP2 could be TP17, and TP3 could be TP15.
• Nucleotide sequences of the PCR primers are listed in Table 4. Usage of each primer in creating particular triplets is indicated. All PCR products were purified following a Qiagen PCR kit protocol. All restriction enzymes were purchased from New England Biolabs. Plasmids were prepared using Qiagen DNA Miniprep kits. All six triplet coding regions were DNA sequenced (SEQ ID NOs: l-6) and amino acid sequences translated (SEQ ID NOs:7-12).
• the assay of the subject invention provides for the measurement of antibodies to three T. pallidum antigens, TP15, TP17 and TP47.
• the assay is performed on antigen precoated microtiter plates. Samples are added to the microtiter plate wells and incubated. T. pallidum IgG/IgM specific antibodies, if present, will bind to and become immobilized by the antigen pre-coated on the wells.
• the bound antibodies were detected either in a direct conjugated antigen sandwich format (see Fig. 18), or in an indirect format detected by conjugated anti-human IgG and IgM (see Fig. 19).
• ELISA high-binding plate well surface as capture antigen The plate was then blocked with 1% BSA/PBS to cover all unbound well surfaces. Syphilis infected patient's serum or plasma was added in wells and incubated for a first incubation period, enabling T. pallidum antibody (IgG, IgM, and IgA) in the sample to react with the precoated triplet antigens. Unbound materials were washed away after the first incubation.
• HRP conjugated recombinant TP triplet was the detector and was added into the wells and incubated for a second incubation period. After the second incubation, unbound triplet conjugates were washed away. The formed antigen - human T.
• pallidum antibody (IgG/IgM) - antigen complex was measured by adding peroxidase substrate solution, then the reaction was stopped after 30 minutes and optical density was recorded for analysis.
• an HRP conjugated mouse monoclonal anti-human IgG and HRP conjugated mouse monoclonal anti-human IgM mixture was the detector and was added into the wells and incubated for the second incubation period. After the second incubation, unbound conjugates were washed away. The formed anti-human IgG/IgM - human T. pallidum antibody (IgG/IgM) - antigen complex was measured by adding peroxidase substrate solution, then the reaction was stopped after 30 minutes and optical density was recorded for analysis.
• the engineered recombinant T. pallidum triplet has a 10 amino acid leader sequence (tag 261) at the N-terminus and two to four amino acid linkers between each TP antigen.
• the tag 261 sequence was derived from human placenta growth factor (P1GF).
• the human copper zinc superoxide dismutase (hSOD) is incorporated at the C-terminus of the T. pallidum antigen triplet to form a fusion protein.
• hSOD has been used previously in various recombinant antigen fusions in diagnostic assays for infectious pathogens such as HCV, HIV etc.
• hSOD is a small size, low immunogenic human endogenous protein, which has 153 amino acids with a molecular weight of about 16kD.
• the 11 lysine residues in hSOD provide extra conjugation site for biotinylation and HRP conjugation.
• Coating buffer (lOmM phosphate, 2mM EDTA, pH 7.0), blocking buffer (1% BSA in PBS, pH 7.0), washing solution (PBS with 0.05% twenn-20), sample buffer (Blocker Casein in PBS with 0.05% tween-20, Pierce)
• ELISA specimen and conjugate diluent Blocker Casein in PBS from Pierce. Tween 20 was added to a final of 0.05% before use. In the direct assay, hSOD lysate was added together with HRP conjugated TP triplet. • Purified recombinant TP triplet fusions, their sequences were validated by DNA sequencing (see SEQ ID NOs:l-6). Proteins were expressed in prokaryotic E.coli cell. Protein purity was validated to be greater than 87% by SDS PAGE.
• HRP conjugate reagent buffer contains: H20, K2HP04 (anhydrous), KH2P04
• HRP horseradish peroxidase
• substrate tablet (0-Phenylenediamine-2HCl)
• solution and stop solution are components from Ortho-Clinical Diagnostics general ELISA products.
• the ELISA Assay Format is shown in Figs. 18 and 19, both a direct assay format and an indirect assay format.
• ELISA Assay Protocol Plate coating: 1) add lOOuL/well coating solution containing 2ug/mL of TP triplet fusion at 25 °C for 18hrs. 2) Wells were washed once with washing buffer and 290uL/well blocking buffer were added for lhr/25°C blocking. 3) After blocking buffer aspirated, plates were dried greater than 4 hrs in a low humidity incubator. 4) Plate was pouched in an air-proof sealed bag until use.
• Direct Assay Protocol Assay: 1) Add 50uL Casein (PBS) specimen diluent and 50uL specimen (or control) to each well. Plate was incubated for 30 min at 37°C with shaking. 2) After 6 times wash with washing solution; add lOOuL HRP conjugated TP triplet fusion diluted in Casein (PBS) to each well. Plate was incubated for 30 min at 37°C with shaking. 3) After 6 times wash, add lOOuL OPD substrate and incubate in dark for 30 min at 25°C. 4) Add 25uL stop solution and read optical density (OD) at 492nm.
• PBS Casein
• OD read optical density
• Indirect Assay Protocol Assay: 1) Add 90uL Casein (PBS) specimen diluent and lOuL specimen (or control) to each well. Plate was incubated for 15 min at 37°C with shaking. 2) After 6 times wash with washing solution; add lOOuL HRP conjugate mixture containing HRP -mouse monoclonal anti-human IgG and HRP -mouse monoclonal anti-human IgM diluted in casein (PBS) to each well. Plate was incubated for 15 min at 37°C with shaking. 3) After 6 times wash, add lOOuL OPD substrate and incubate in dark for 30 min at 25°C. 4) Add 25uL stop solution and read optical density (OD) at 492nm.
• PBS Casein
• ELISA Reaction (1) Wells were coated with a serial dilution of six TP triplets and post-coated with 1% BSA in PBS. (2) Add lOOul HRP conjugated mouse monoclonal anti-261 tag diluted in Casein (PBS) to antigen precoated wells, and incubate at 37°C for 15 minutes with shaking. (2) Wash 6 times, add lOOuL OPD substrate solution, and incubate at RT for 15 min in dark. (4) Add 25uL 4N sulfuric acid stop solution and read at 490nm.
• Results shown in Table 1 were ODs.
• Proposed TP Triplet coating concentrations were derived from calculation to calibrate antigen quantity immobilized on the plate and used in plate coating in the antibody assay evaluation.
• ELISA Reaction (1) Wells were coated with six TP triplets at a concentration defined in Table-1, and post-coated with 1% BSA in PBS. (2) Add 50ul Casein (PBS) and 50ul panel specimens to antigen precoated wells, and incubate at 37°C for 15 minutes with shaking. (3) Wash 6 times, add 100 ul HRP conjugated TP triplet antigens, and incubate at 37°C for 15 minutes with shaking. HRP conjugated antigen is the antigen coated on the plates. (4) Wash 6 times, add lOOuL OPD substrate solution, and incubate at RT for 15 min in dark. (4) Add 25uL 4N sulfuric acid stop solution and read at 490nm.
• Results shown in Table 2 were S/C values. S is OD signal, C is cut-off, equals 5 times of an average OD given by three negative controls.
• ELISA Reaction (1) Add 90ul Casein and lOul panel sample (2 fold serial diluted in normal human plasma) to antigen precoated wells, and incubate at 37°C for 15 minutes with shaking. (2) Wash 6 times, add 100 ul conjugate mixture containing HRP mouse monoclonal anti-human IgG and monoclonal anti-human IgM, and incubate at 37°C for 15 minutes with shaking. (3) Wash 6 times, add lOOuL OPD substrate solution, and incubate at RT for 1 minutes in dark. (4) Add 25uL 4N sulfuric acid stop solution and read at 490nm.
• the cut-off is 5 times of an average OD given by three negative controls.
• TP47 triplet construct are as described above and as shown in Fig. 1.
• a kit is provided which includes a reagent pack and a calibrator.
• the reagent pack contains: 100 coated wells (streptavidin, bacterial; binds >2 ng biotin/well); 13.1 mL biotinylated antigen reagent (biotin-recombinant TP antigens 0.1 ug/mL) in buffer with bovine gamma globulin, bovine serum albumin, and antimicrobial agent; and 20.4 mL conjugate reagent (HRP -recombinant TP antigens, 0.15 ug/mL) in buffer with bovine serum albumin and antimicrobial agent).
• the calibrator contains VITROS ® Syphilis TPA Calibrator (human syphilis IgG positive plasma, 2.2 mL) with antimicrobial agent. The test uses 25 uL of calibrator for each determination.
• Suitable specimens for use with the test are serum, heparin plasma, EDTA plasma, and citrate plasma.
• the test uses 25 uL of sample (specimen) for each determination.
• the test also uses signal reagent (such as VITROS ® Immunodiagnostic
• wash reagent such as VITROS ® Immunodiagnostic Products
• Results are automatically calculated by the VITROS ® Immunodiagnostic and VITROS ® Integrated Systems, and represent "signal for test sample'Vsignal at cutoff (cutoff value)". Samples with results of ⁇ 0.80 will be flagged as "negative”, samples with results >0.80 and ⁇ 1.20 will be flagged as "borderline”, and samples with results >1.20 will be flagged as "reactive”. Negative indicates no active or previous infection with Treponema pallidum; borderline indicates the test is unable to determine if
• Treponema pallidum infection has occurred, and the sample should be re-tested; and reactive indicates active or previous infection with Treponema pallidum.
• VITROS ® Syphilis TPA Test Referring to Table 5, initial sensitivity and specificity was assessed on a population of 4290 samples using the VITROS ® Syphilis TPA test and a commercially available immunoassay ("IA 1") for antibodies to Treponema pallidum. An initial analysis in the VITROS ® Syphilis TPA test gave an initial specificity, including borderline samples (4015/4016) of 99.98% (exact 95% CI 99.9-100.0%). Initial sensitivity, including borderline samples (266/274) was 97.08%> (exact 95% CI 94.3- 98.7%). One (0.025%) sample was borderline in the VITROS ® Syphilis TPA test. The commercially available test did not have a borderline region.
• Results showed precision for samples at the cut off up to strong positives averaged 1.6 % (range 0.9 - 3.2%) within run, 4.8% (range 2.7 - 9.0%) within calibration, and 4.6% (range 2.1 - 9.0%) within lab.
• the VITROS ® Syphilis TPA test thus gives excellent precision across the borderline and reactive ranges, on all VITROS ® systems.
• VITROS ® Syphilis TPA test was evaluated for interference. Of the compounds tested, none was found to interference with the clinical interpretation of the test at the concentration indicated. [0089] The VITROS ® Syphilis TPA test was also evaluated with two sets of proficiency samples from CAP and NEQAS and two commercially available
• Syphilis TPA test combines good analytical and clinical performance with the operational simplicity of a rapid automated continuous random access immunoassay.
• F4-ER SEO ID NO: 13 cacaGAATTCATTAAAGAGGAGAAATTAAC
• a TP15-BG SEO ID NO: 16 agctggAGATCTCGGGCCGCGAGAGATAATGGCTTCTT
• TP15-BG2 SEO ID NO: 17: gctggAGATCTACCGCGAGAGATAATGGCTTCTT
• TP17-BG SEO ID NO: 18 agctggAGATCTCGGGCCTTTCTTGGTTTTCTTCAGAACGTA
• TP47-BG2 SEO ID NO: 19: agctggAGATCTTGGACCCTGCGCCACCACTTTCGCG
• T17-BH SEQ ID NO:22 GTGAGCTGCACCACGGT
• F-47b SEQ ID NO:24 GGTTAGCGATCAGGCCGT
• RS SEQ ID NO:29 TGCAGTCGACGGGCCCGGGAT
• T15-Sac SEO ID NO:30 CGCGACCGTGAGCTCTCAGAGTTTT
• TP17-EAG SEO ID NO:31 CCCTGCCGGCCGCAGATTGT
• RS-H3 SEO ID NO:33 agccAAGCTTcattaCTGGGCGATACCAATAACGCCA Table 5

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